NosocomialSerratia marcescensInfections Associated With Extrinsic Contamination of a Liquid Nonmedicated Soap

Objective:To determine the role of nonmedicated soap as a source ofSerratia marcescensnosocomial infections (NIs) in hospital units with endemicS marcescensNI and to examine the mechanisms of soap colonization.Setting:University-affiliated tertiary-care hospitals.Methods:A prospective case-control study and an environmental investigation were performed to assess the relationship betweenS marcescensNIs in hospital units andS marcescens-contaminated soap. Soap-bottle use and handwashing practices were reviewed. Cultures of healthcare workers’ (HCWs) hands were obtained before and after hand washing with soap.Results:5 of 7 hospital units withS marcescensNIs had soap bottles contaminated withS marcescens, compared to 1 of 14 other units (P=.006). After hand washing with anS marcescens-contaminated soap pump, HCWs' hands were 54 times more likely to be contaminated withS marcescens(PConclusions:Extrinsic contamination of a non-medicated liquid soap byS marcescensresulted in handborne transmission ofS marcescensNIs by HCWs in our setting. This finding led to the application of strict guidelines for nonmedicated soap use and to the reinforcement of alcoholic hand disinfection.